Cognitive approaches to the problems of declining memory in the normally-aging population have proceeded largely independently of neurobiological investigations of age-related changes in brain structures and processes. The proposed research combines these two approaches in order to explore directly the relations between changes in neural structures and the cognitive/behavioral changes that occur with age. In recent years it has become evident that memory is not a unitary function, but is composed of different systems and processes, some affected by aging and brain damage and others not. Understanding the nature of these processes and their neural correlates will enable us to develop rehabilitation techniques that target specific areas of deficit and at the same time take advantage of specific areas of strength within an individual. Most studies of aging compare a randomly selected group of older adults to a group of young adults. Such comparisons, however, fail to take into account the heterogeneity of the elderly population. The investigators' research program specifically focuses on individual differences by categorizing older individuals according to their performance on groups of neuropsychological tests thought to tap functions associated with either prefrontal or medial temporal cortex. The composite scores of neuropsychological function are then used as predictors in all behavioral experiments and in electrophysiological studies that examine event-related potentials in related paradigms. A subset of the elderly individuals will also receive magnetic resonance imaging (MRI) of the brain regions thought to be implicated in different kinds of memory in order to confirm the relations between cognitive and brain function. Research will focus on the differences between memory for the content of an experience and memory for its context, often referred to as source memory. Older adults show a disproportionate deficit in source memory, which has been hypothesized to be due to declining frontal lobe function. Other research suggests that the medial temporal lobes are critical for the binding of various attributes of an experience into a coherent memory trace. The investigators' goal is to differentiate the contributions of these two brain regions to source and item memory and to document their differential impact on age related memory decline. The proposed experiments include several context/source manipulations--perceptual, spatial, temporal, and internal vs external--across a range of materials--verbal, nonverbal, auditory, visual, novel and familiar. In each study, comparisons will be made not only between older and younger adults, but also among subgroups of older adults according to their putative frontal and medial temporal functioning. Issues to be addressed include: the extent to which age-related memory deficits are attributable to problems of encoding, retrieval or both, the role of interference in source attributions, and the dissociation between explicit and implicit memory for source.